DESCRIPTION: Stem cells are emerging as a powerful biomedical tool, and significant applications in drug/toxin screening, disease modeling, and clinical cell therapy are on the horizon. Recent studies have pushed stem cells closer to biomedical applications by improving stem cell biomanufacturing processes, including cell expansion, differentiation and tissue morphogenesis. However, the need for costly and poorly defined biological supplements such as recombinant growth factors (GFs) remains a prohibitive challenge. GF supplements can represent more than half of the cost of stem cell biomanufacturing processes in emerging applications, and existing processes remain dependent on complex, poorly defined GF-binding matrices such as Matrigel. Remarkably, while the current paradigm involves bombarding stem cells with concentrated GF- containing supplements, many of the relevant GFs in stem cell biomanufacturing are already routinely produced by the stem cells themselves. There is an opportunity to shift the current paradigm by capturing cell- secreted GFs, leading to less costly and more well-defined stem cell biomanufacturing. Context: Our initial funding period (7/1/2009-6/30/2014) established new mechanisms for specific GF sequestering, and produced 33 manuscripts, 8 patent applications, and 5 technology licenses to industry partners. We discovered that biomaterials engineered with biomimetic peptides could regulate specific GF signaling in adult cell culture. During the next funding period we will use our defined GF sequestering concept to circumvent critical barriers in biomedical applications of stem cells. A central, provocative question driving the next funding period is: can engineered biomaterials control GF-dependent stem cell expansion, differentiation, and morphogenesis without delivering any GFs? Specific Aims: Specific Aim 1 will use biomaterials to sequester cell-secreted GFs and amplify human mesenchymal stem cell expansion and differentiation. Specific Aim 2 will use biomaterials to locally regulate specific GF activity in human induced pluripotent stem cell culture, and thereby enhance production of stem cell-derived endothelial cells. Specific Aim 3 will develop biomaterials that can selectively control paracrine signaling during vascular morphogenesis in vitro and in vivo. Innovation: Our proposed studies will establish synthetic biomaterials as defined mediators of endogenous, recombinant, and paracrine GF signaling. Significance: Our proposed studies will mitigate the need for expensive and complex biological supplements that currently hinder biomedical applications of stem cells. The resulting approach will be transformative, as GF supplements represent the primary driving force for increased cost and regulatory burden in stem cell applications.